This invention relates to automatic chemical analysis and more particularly, but not exclusively, is concerned with apparatus including modular units for carrying out chemical analyses automatically.
Various types of analytical apparatus are known. One type of apparatus is known as a discrete analyser, and in this apparatus a sample is placed in an individual container where, in general, it remains for the duration of the analytical procedure which is carried out. An advantage of this arrangement is that each discrete sample can be individually labelled, so that confusion between different samples is minimised.
In a further type of apparatus, samples travel continuously, or quasi-continuously, in a carrier stream moving along a narrow flow channel which is designed so that each individual sample retains its integrity with respect to adjacent samples. In certain previous systems, slugs of air have been used to separate individual samples in the moving stream. In other systems, the carrier medium is the reagent with which the individual samples are to react.
European Patent Specification No. 0047130 describes a method of analysis of a liquid sample which is carried along a flow channel by a carrier liquid, which method comprises simultaneously extracting by aspiration from separate containers a predetermined quantity of a given sample and a predetermined quantity of a selected reagent therefor; bringing the extracted sample and the extracted reagent together; and causing the sample/reagent mixture to travel along said flow channel as a discrete liquid slug interposed in the stream of carrier liquid to the measurement cell of an analytical instrument. This method can be used in the sequential analysis of a series of samples, and can operate either with a plurality of samples simultaneously present at different positions within the flow channel, or with just a single sample in the flow channel at any one time. Also, the method of European Patent Specification No. 0047130 does not involve the use of air bubbles to segment the carrier liquid. Thus the material present in the flow channel is in the form of a continuous liquid, the carrier liquid having interposed therein discrete liquid slugs of sample/reagent mixture, which can conveniently be termed "active slugs". Conveniently in this method, the carrier liquid is deionized water.
The present invention is concerned with analysis apparatus which can be used to carry out the method described in European Patent Specification No. 0047130. The apparatus of the present invention, however, is not limited to such use; other analytical procedures can equally well be carried out using the apparatus of this invention.